Date of Award
M.S. in Engineering Science
Geology and Geological Engineering
Gregg R. Davidson
The double-porosity Generalized Radial Transport (GRT) model is an extension of the generalized radial flow approach developed for hydraulic test interpretation. In both approaches, a flow dimension characterizes the change in flow area versus radial distance from the borehole. The GRT model collapses to a 1D, radial, and spherical advection dispersion equation (ADE) for integer flow dimensions of 1, 2, and 3, respectively. And, the model also transforms to sub-linear, sub-radial, sub-spherical and eventually transform to super-spherical transport model for non-integer flow dimension, n of 0 < n < 1, 1 < n < 2, 2 < n < 3 and n >3 respectively. Non-integer flow dimensions, especially sub-radial, are commonly reported from pumping tests in fractured rock systems and can be linked with aquifer geometry and heterogeneity. We consider the impact of sub-radial flow dimensions on convergent flow tracer tests in fractured rock. In comparison to radial transport, sub-radial transport leads to higher velocities, much earlier arrival times, and higher peak concentrations in breakthrough curves. Faster advective transport leads to less diffusion into fracture-bounded matrix blocks and steeper slopes of late time concentrations. Larger blocks, corresponding to slower diffusion rates, are undersampled. Transport and diffusion parameters estimated from sub-radial tracer tests using a radial ADE will lead to underestimates of dispersivity and diffusive capacity and overestimates of diffusion rate. Then, we compare the results of double porosity, radial transport and GRT interpretations of convergent flow tests conducted in a fractured dolomite in southeastern New Mexico.
Mamud, Md Lal, "Generalized Radial Transport Model for Interpreting Convergent Flow Tracer Tests in Fractured Rock" (2019). Electronic Theses and Dissertations. 1632.